Stator for two speed induction type motor



March 2l, 1967 A. A. BRAMMERLO ETAL. Re- 25,179

STATOR FOR TWO SPEED INDUCTION TYPE MOTOR Original Filed Sept. 28, 1962ngz.

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United States Patent O 26,179 STATGR FOR TWO SPEED INDUCTION TYPE MOTORAllen A. Brammerlo, Sycamore, and Harold C. Stout, De Kaib, Ill.,assignors to General Electric Company, a corporation of New YorkOriginal No. 3,153,183, dated Oct. 13, 1964, Ser. No. 226,894, Sept. 28,1962. Application for reissue Oct. 6, 1966, Ser. No. 589,174

7 Claims. (Cl. S18-224) lWatter enclosed in heavy brackets [I appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

Our invention relates to alternating current inductien motors and moreparticularly to an improved stator arrangement for use in single phasemotors adapted to operate selectively at two different speeds.

Accordingly, it is a general object of the present invention to providean improved stator for use in a two speed electric motor, and it is amore specilic object to provide an improved stator having a windingarrangement capable of providing selective two speed operation.

It is another object of the invention to provide an improved stator foruse in a two speed electric motor in which the stator includes a corehaving magnetic sections related to both of the operating speeds andrunning poles produced by the stator windings.

lt is still another object of the invention to provide an improved twospeed motor stator which permits economies in its manufacture withoutadversely affecting motor performance.

in carrying out the objects in one form, we provide an improved statorarrangement for use in an alternating current split phase two-speedinduction motor in which the stator includes a magnetic core andwindings for achieving two speed selective motor operation. The coreincludes a yoke section and a plurality of angularly spaced apart teethsections of differing cross section widths projecting inwardly from theyoke section to detine a plurality of slots, these slots accommodate afirst and second main winding, each `formed of a number of concentriccoils, with the tirst winding providing four primary magnetic runningpoles for operating the motor at high speed. The coils in one ofthe fourrunning poles are connected to the second winding in series relation forenergization therewith, and are acconfrmodated in the same slots as someof the second winding coils such that the common slotted" coils arearranged in additive magnetic relation to produce augmenting MJM.F.s(magnetomotive force).

The additive serially connected coils and the remaining coils of thesecond main winding, when energi7ed, form six running poles to eiiectthe low speed operation. The depth of the yoke section is generallyrelated to the total flux generated by the four running poles and is ofmaximum depth in the regions directly over the slots at `the extremitiesof each of the four poles where the total iiux is greatest. This depthis more than sufficient to transmit the total iiux generated during siXpole operation.

`On the other hand, the cross section width of the teeth sections aregreatest near the center of each of the six running poles and readilytransmit the total tiux in both speeds of operation. Among otheradvantages and features, with this arrangement it is possible to achievegeneral symmetry for both the windings and the core and to provide adesirable slot space factor for receiving the windings in spite of thefact that the stator is wound for two speed operation. By the presentinvention, economy of manufacture may be realized with- Out anydetrimental effect on performance of the motor.

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The subject matter which we regard as our invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. iOur invention, itself, however, both as to itsorganization and method of operation, `together with further objects andadvantages thereof may best be understood by reference to the followingdescription taken in connection with the accompanying drawing.

In the drawing:

FIG. l is a schematic end view of a stator of a single phase motorincluding the preferred embodiment of the present invention tas appliedto a motor adapted to operate selectively on either four or six runningpoles; and

FIG. 2 is a schematic circuit diagram for the stator of FIG. 1 showingthe selective connection of the individual coils for the four and siXpole operation.

Turning now to the drawing in more detail, for purposes of explanationour invention is illustrated as being incorporated in a stator l0 ofgenerally square peripheral configuration with curved corners capable ofproviding two speed operation in an alternating current single phasesplit phase induction motor. The motor may include a rotor formed with astandard skewed squirrelcage secondary winding in the usual way. Therotor is indicated by number 11 in FIG. 2 where it is sehematicallyshown. The stator includes a core l2 built of a preselected number oflaminations punched from relatively thin magnetic sheet material, suchas common iron. The laminations are conventionally secured together injuxtaposition by four spaced apart keys 13 frictionally received incomplementing aligned notches `1li provided near each corner of thecore.

As illustrated, the stator core is furnished with thirtyfour spacedapart teeth sections 15, each having generally parallel sides, whichproject inwardly from an integral yoke section 16, to dene a number ofwinding slots 17 and slot entrances 18 at the rotor receiving bore,These slots have top edges provided generally parallel to the outer edgeof the core and accommodate two main windings, identified respectivelyby numerals 19 and 20, which form the primary running poles for theselective two speed operation of the motor. By an important aspect ofthis invention, the yoke and teeth sections are individually related inconstruction to the respective running poles created by main windings 19and 2t) for the two speed operation. ln the drawing, the radial centersof the four running poles are denoted by characters S1, N2, S3 and N4while the radial centers of the six running poles have `been indicatedat S11, N12, N14, S15 and N16. More specifically, we relate the size orradial cross sectional depth of the yoke section directly above theslots primarily to the total flux generated by the high speed operationand relate the size of the teeth sections to the total iiux createdduring low speed running conditions.

ln order to describe the manner in which windings 19 and 2i) provide thefour-six pole selective operation and the structural relation of thecore thereto in the illustrated embodiment of the invention, we haveidentified the thirty-four teeth sections by numbers 2t1-55 inclusive inFIG. l. In addition, since the illustrated yoke section is symmetricalabout {S1-S3 as well as in other respects to be explained later, forreasons of simplicity, only the yoke regions directly over one half ofthe winding slots in FIG. 1 have been referenced, numbers 61-77inclusive.

Turning now to main `winding 19, it includes four concentric groups ofcoils, A, B, C, and D, with each group being similarly formed by threecoils 78, 79, and 80 spanning, in effect, four, six, and eight teethrcspectively. The number of turns of wire for each pole any he chosen toapproximate a sinusoidal wave form for the flux distribution in the fourrunning poles and to provide Nihil? balance between thc four poles.Normally, a core carrying a winding which provides four pole operationwith thirty-six equally and angularly spaced apart slot entrances orteeth. In core 12, the slot entrances 18 are equally spaced apart (tendegrees) with the exception of the entrances adjacent teeth 2l and 38which are twenty degrees apart. In the illustrated core. the eliminationof two conventional slots is permitted and two teeth of enlarged widthmay be provided.

With respect to main winding 20, it includes six groups of coils, a, b,c, d, and three serially interconnected with the coils of group A forwinding 19, which together effect six pole motor operation when mainwinding 2l) is energized. FYG. 2 shows in diagrammatic form one circuitfor achieving four-six pole operation.

In the motor of the exemplitication, main winding 19 is energized duringstarting conditions for both speeds of operation. To assist in starting,a start winding 81, having four groups of concentric coils 82, 83, and84 wound on the core, is angularly displaced by ninety electricaldegrees from main winding 19.

The circuit revealed by the solid lines in FIG. 2 displays the windingarangement under high speed starting conditions. During this condition,main winding 19 and start winding 81 are energized in parallel acrossA.C. power source 85, through lines 86, 87 and speed selector switch 90.That is, main winding 19 is excited from line 86 through conductor 91attached to the high speed side 92 of switch 90 of the singlepole-double throw variety, through the selector arm 93 of switch 90 andhence to line 87. With respect to the start winding, it is connectedbetween switch 90 and line 86 through Contact sides 94 and 95, closed bymovable arm 96 of a centrifugally operated switch 98. When the motorcomes up to high speed, a standard centrifugal mechanism 99, operativelyconnected to switch 98, moves arm 96 to the position indicated by thebroken lines, in engagement with switch side 97, thereby deenergizingstart winding 81. Consequently, high speed running operation is providedby the four running poles created by excited main winding 19.

To cease motor operation, selector switch arm 93 is moved to the "ott"position and centrifugal mechanism 99 will return movable arm 96 to theunactuated position, closing contact sides 94 and 95 of switch 98. Forstarting the motor Linder low speed conditions, movement of selectorswitch arm 93 to the low speed side 102 of speed selector switch 90 willestablish a parallel circuit of the start and main winding 80 and 19,between lines 86, S7.

After the motor reaches the speed at which centrifugal mechanism 99actuates arm 96 into contacting engagement with switch side 97, polesN1, S3, and N4 of winding 19 and the entire start winding St) will bedisconnected from the power source, leaving only the coils of pole S1 ofmain winding 19 energized in series circuit relation with the nowexcited main winding 20, the connection being indicated at 104. It willbe seen from FIG. l that the coils of group A, are disposed on the coresuch that their radial center is common with the radial center of thecoils of group "a" for winding 20, and certain coil sides of cach groupare accommodated in the same slots. With the current owing through thecoils as shown by the arrows in the drawings, that is, in the samerelative direction through the "common slotted coils of coil groups aand A for the respective main windings, and in an alternate directionthrough coil groups b, c, d, e, and f of winding 20, six primary runningpoles will be formed in the manner most clearly revealed in FIG. 1.Coils in coil groups "a" and A which are located in the common slotswill in effect be in additive magnetic relation and produce augmentingM.ivt.F.`s (magnctomotive force). This allows the common slotted coilsol coil group "a" to include less wire turns than the correspondingcoils in groups c and c, and still provide f-ix pole symmetry in lothwire turns and coil deployment when the number of turns for the sixrunning poles are properly chosen.

Still referring to FlG. l, in accordance with one aspect of ourinvention, the yoke section preferably is of minimum magnetic depth inthe regions directly above the slots at the center of each of the tourrunning poles S1, N2, S3, and N1 and progressively increases in depth toa maximum dimension at the pole extremities. We prefer to relate theseyoke regions to the total lilies of ux generated by main winding 19under running conditions, the strength of the flux in the yoke sectionbeing greater at the pole extremities. In addition, it is preferablethat each yoke region is just under the saturation point at theselocations. The total flux generated in the yoke section at each of thefour ruiming poles will be, in most instances, of higher intensity atthe same yoke region for that created at the six running poles S11, N12,S13. N11, S15 and N111 during low speed running conditions. Thus, theyoke cross section depth at any given yoke region should, generallyspeaking, be more than sufficient to accommodate the toal ux of the sixruiming poles. In the core shown in FIG. 1, yoke section l2 thereforegradually increases in width directly over the slots from a minimumvalue at regions 'itl for poles N2 and N4 and 77 at poles S1, S3. to amaximum dimension at regions 64, 65, 73 and 74 located at each extremityof the four poles.

In a somewhat converse manner, we provide the teeth adjacent the centerof each of the six primary running poles with the largest cross sectionwidths, at any given radius, and in the preferred form, the teethprogressively decrease in width from the greatest dimension near thecenter of each of the six poles to a minimum value adjacent each ofthesix pole extremities shown in FIG. l by arrows and radial lines in therotor bore. This arrangement, in actual practice, has proven to be verysatisfactory for transmitting the llux generated by the windings underboth motor operating speeds. For instance, in one motor statorconstructed in accordance with FIG. l, teeth 32, 33, 43, 44, 49, and 50each included approximately 30,000 total lines of: flux for six poleoperation, but slightly less than that when winding 19 was energized toetlcect four pole running conditions. Enlarged teeth 21 and 38 includedabout double that flux total under four pole running speed, the examplemotor had a rated speed of 1725 r.p.m. with a breakdown torque of 45 o2.feet. At six pole operation (low speed) its breakdown torque was 41 oz.feet and a rated speed of 114D rpm.

The construction of the present invention not only provides enhancedperformance at both selective speeds of operation, but in additionallows economics in manufacture. For instance, it is possible toconstruct the core of the illustrated and preferred embodiment withgeneral quadrature symmetry in both yoke and teeth sections for reasonsof manufacturing economy while still retailiing the performance beneiitsof our invention iii both speeds ol` operation. For convenience ofpresentation, example dimensions will be used for the quadrature lyingangularly between NZ-Sg sct out below in tabulated form:

"icclli Sections Example. Example Number til Fig. 1 dimensions Niiinlicriii Fig. 1 diiiieilsioiis iii inches in inches .lilla 3U. s .14S

.35a Ill. 148

.fitti 3 .103

.435 g at... .14s

.425 l :in 134 3M b t' i ot tooth) c lllll All of the winding receivingslots are formed with sucient winding accommodating area to receive thecoils of the three windings, to realize economy and ease in windingplacement. Thus, the slot space factor, an indication of the diiculty ofdistributing the winding turns in the slots can readily be maintainedbelow 60%.

It will be appreciated, of course, that the most desirable dimensionsand optimum relationships of the individual yoke regions and teethsections will be governed by the flux saturation characteristics of themagnetic material used, the exact windings employed and the overall sizeof the motor. Moreover, the foregoing optimum yoke and teethrelationships may be varied while still obtaining the advantages of ourinvention. Furthermore, while our improved stator construction has beenshown as embodied in a stator wound for four and six pole selectiveoperation, it should be appreciated from the foregoing by those skilledin the art that the principles of the invention are equally applicableto other two speed polar arrangements. Likewise, of course, theinventive concepts disclosed above may, if desired, be incorporated instator cores having circular rather than rectangular configurations.

It will therefore be apparent to those skilled in the art, that while wehave shown and described what at present is considered to be thepreferred embodiment of our invention in accordance with the patentstatutes, changes may be made in the structure disclosed withoutactually departing from the true spirit and scope of this invention, andwe therefore intend to cover in the following claims all such equivalentvariations as fall within the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. In a single phase induction type motor for operation selectively attwo speeds, a stator including magnetic core comprising a yoke sectionand a plurality of angularly spaced apart teeth sections togetherdefining a number of slots; a first main winding comprising a pluralityof coils positioned in said slots to form at least two primary magneticrunning poles for operating the motor at one speed; a second mainwinding having a plurality of coils positioned in said slots; at least apart of the coils in one primary running pole of said first windingconnected in series relation with said second winding for energizationtherewith; said last-mentioned coils of said one pole being locate-d inthe same slots of the core as coils of said second main winding andbeing arranged in additive magnetic relation therewith when said secondwinding is energized; said additive serially connected coils of bothwindings, together with the remaining coils of said second winding,defining an even number of primary running poles in excess of the numberofthe first winding running poles; the yoke section having a minimummagnetic depth in the region directly over the slots near the center ofeach of the lesser number of running poles and a maximum depth adjacentthe region directly over the slots near the extremities of each of saidlast-mentioned poles; and the teeth sections located adjacent therespective centers of the higher number of running poles being greaterin width than those respectively located at the extremities of the samepoles.

2. In a single phase induction type motor for operation selectively attwo speeds, a stator including a magnetic core comprising a yoke sectionand a plurality of angularly spaced apart teeth sections of dilieringwidths delining a number of slots; a first and second main winding, eachcomprised of a plurality of coils, positioned in said slots to formselectively at least two primary running poles and a greater even numberof primary running poles of alternating polarity for operating the motorat either of two speeds; said yoke section having a maximum depth in theregions directly over the slots near the extremities of each of thelesser number of primary running poles; and said teeth sections locatedadjacent the respective pole centers of said greater even number ofrunning poles being greater in width than those respectively positionedat the extremities of the same poles.

3. In a single phase induction type motor for operation selectively attwo speeds, a stator including a magnetic core comprising a yoke sectionand a plurality of angularly spaced apart teeth sections projectinginwardly from the yoke section to define a corresponding number ofslots; a rst main winding comprising a plurality of coils positioned insaid slots; a second main winding having coils disposed in said slots;said [windngs] windings selectively forming at least two running polesand an even number of running poles of alternating polarity in excess ofthe rst mentioned poles for operating the motor at either of two speeds;said yoke section having a maximum depth in the regions directly overthe slots near each of the extremities of the lesser number of runningpoles; and said [teech] teeth sections generally varying in crosssection widths from a minimum near the extremities of the greater numberof running poles to a maximum adjacent the centers of saidlast-mentioned running poles.

4. In a single phase induction type motor for operation selectively attwo speeds, a stator including a [inagnectic] magnetic core comprising ayoke section and thirty-four angularly spaced apart teeth sections ofvarying widths projecting inwardly from the yoke section to definethirty-four slots two diametrically disposed teeth being substantiallygreater in width than the remainder of the teeth sections; lirst andsecond main windings each comprising a plurality of coils positioned insaid slots; said windings arranged to form selectively four and sixrunning poles of alternating polarity for operating the `motor at eitherof two speeds; a start winding having coils concentrically disposed insaid slots electrically displaced from said first main winding, with oneside of the outer coils accommodated in the slots adjacent thesubstantially larger teeth; [said yoke section having a minimum magneticdepth in the region directly over the slots near the center of each ofthe four running poles and a maximum depth adjacent the yoke regiondirectly over the slots adjacent the outer portions of the same poles;]and said larger teeth sections being located at the pole centers for twoof each of the four and six running poles, with the teeth sectionsprogressively increasing in width from a minimum adjacent the poleextremities of the six running poles to a maximum near the radialcenters of the same poles.

5. In a single phase induction type motor for operation selectively attwo speeds, a magnetic core comprising a yoke section and a plurality ofangularly spaced apart teeth forming a number of slots; a first mainwinding positioned in said slots to form four primary magnetic runningpoles of alternating polarity for operating the motor at one speed; eachof said poles comprising a plurality of concentrically distributedcoils; a second main winding having a number of coils positioned in saidslots to form a plurality of coil groups with more than one group havingconcentrically arranged coils', the concentric coils of one pole of saidrst winding connected in series relation with said second winding forenergization therewith and carried in the same slots as the concentriccoils of one of said coil groups of said second winding, with the radialcenters for the respective concentric coils being approximately common;said last-mentioned concentric coils for both windings arranged inadditive magnetic relation to provide a running pole of the samepolarity adjacent said radial centers when said second winding isenergized; said additive serially connected concentric coils, togetherwith the other coils of said second winding, delining six primaryrunning poles for operating the motor at a second. speed; [the yokesection of said core generally increasing in magnetic depth in theregions over the slots, from a minimum dimension near the centers of thefour poles to a maximum adjacent each of the four pole extremities;] andthe teeth sections of said core located near the center of cach of thesix running poles being of greater cross section than the teeth sectionsadjacent the extremities of each of the six poles.

6. In a single phase induction type motor for operation selectively atmore than one speed, a stator including a magnetic core comprising ayoke section and a plurality of angular-l)| .spaced apart teeth sectionsprojecting inwardly from the yohe section to define a correspondingnumber of slots; a plurality of coils positioned in said slotsselectively forming a jrst number of running poles greater than one anda second number of running poles in excess of said )rst number ofrunning poles for operatingr the motor at least at either of two speeds;and said teeth sections generally Varying in cross section width in saidsecond nntnber of running poles with the teeth sections near theextremities of' said second number of rnnning poles being of less widththan those adjacent the polar centers; at least one of the teethsections of two of said first number of running poles being located nearthe polar centers thereof and haring a width greater than the width ofthe teeth sections disposed adjacent the extremities for the same tworunning poles.

7. In a single phase induction type motor for operation selectively atmore than one speed, a stator including a magnetic core comprising ayoke section and thirty-four angularly spaced apart teeth sectionsprojecting inwardly from the yoke section to 'denne thirty-four slots,two diantetrically disposed teeth sections being substantially greaterin width than the remainder of tlte teeth sections; a plurality of coilspositioned in said slot to form selectively at least four and sixrunning poles of alternating polarity for operating the motor at eitherof two speeds; a start winding having coils concentrically dispo-sed insaid slots to form poles electrically displaced from said four runningpoles; the greater-in-width teeth sections being located at the polecenters for two of each of the foar and six running poles, with theteeth sections next adjacent said greater-in-width teeth sections eachhaving a larger width than those located adjacent the pole extremitiesin the sante poles for said six running poles.

No references cited.

ORIS L. RADER, Primary Examiner.

C. E. ROHRER, G. Z. RUBINSON, Assistant Examiners.

